Inhibition by Ca2+ of inositol trisphosphate-mediated Ca2+ liberation: a possible mechanism for oscillatory release of Ca2+.
Light-flash photolysis of caged inositol 1,4,5-trisphosphate (InsP3) was used to generate reproducible transients of free InsP3 in Xenopus oocytes, and the resulting liberation of Ca2+ from intracellular stores was monitored by recording Ca2+-activated membrane currents and by use of the fluorescent Ca2+ indicator fluo-3. InsP3-mediated Ca2+ release was inhibited by elevating the intracellular free Ca2+ level, either by microinjecting Ca2+ into the cell or by applying conditioning light flashes to liberate Ca2+. This inhibition followed a slow time course, being maximal after about 2 s and subsequently declining over several seconds. Negative feedback of Ca2+ ions on InsP3-mediated Ca2+ liberation may explain the oscillatory release of Ca2+ seen during activation of inositol phospholipid signaling in the oocyte, and the time course of the inhibition is consistent with the period of the oscillations.
Parker
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Department of Psychobiology, University of California, Irvine 92715.
Ivorra
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D000204:Activity Cycles; D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D004553:Electric Conductivity; D005260:Female; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000528:radiation effects; D009865:Oocytes / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010782:Photolysis; D015290:Second Messenger Systems; D013997:Time Factors; D014466:Ultraviolet Rays; D014982:Xenopus laevis
D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium